With only 20% of Irish soils at optimum fertility levels, it is important to improve overall soil health while also building soil phosphorus (P) and potassium (K) levels.

Organic manures can help to increase soil organic matter and biological activity while providing major nutrients.

Teagasc’s Mark Plunkett commented at the recent spring tillage seminar that 1,000 gallons of pig slurry can provide nutrients equivalent to a 50kg bag of 19:7:20.

Poultry manure (layers) is often higher in P and K. One tonne of broiler manure, for example, can contain the equivalent of a bag of 11:12:24.

Layers manure can be higher in nitrogen (N) but lower in P.

Mark noted that from 30% to 100% of a cereal crop’s P and K requirement and up to 60% of its N requirement can be replaced using organic manures, so where a source is available nearby it is a good option to consider.

He added that in order to retain N, it is important that slurry is well agitated, evenly spread and is incorporated quickly.

Another essential job is to test the organic manure for nutrient content to ensure the correct rate is applied. If high rates are applied, management problems such as lodging can occur.

Farmer view

Two Co Cork farmers shared their experiences with organic manures at the seminar. Where poultry manure (layers) is applied, Craig Hill can supply all of his spring cereal’s P and K requirements and balances out the N requirement with bagged fertiliser. Craig noted that his soil is in good condition and earthworm numbers are high.

Raymond Moloney started to apply pig slurry to his cereal crops when he lost sugar beet from his rotation. He noted that it has allowed continuous cereals to be grown on the farm. Pig slurry has significantly reduced his dependence on compound fertiliser to supply P and K to his soil.